Before you can access the raycasthitinfo object you need to actually cast a ray. Your script needs some more lines

RaycastHit rayCastHitInfo;
if(Physics.Raycast(origin,direction,rayCastHitInfo))
{
    //here comes your code
}

Read the scripting reference for futher information.

It may have to do with when or how you are getting your GameObject or when or where you are calling the functions or even just how you're testing whether the function is being called. Without more information like a more complete section of script, it is impossible to guess.

I just tested this setup and it works:

CameraPicker.js

var hit : RaycastHit;

function Update() {
    if(Input.GetMouseButtonUp(0) &&
        Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition),hit)) {
        hit.collider.gameObject.SendMessage("Test");
    }
}

Selectable.js

function Test () {
    Debug.Log(gameObject.name);
}

If this does not address your issue, please include more information as it is likely some other part of your script that is not behaving as you expect.